A roller brake test (RBT) is a controlled method used to measure the braking performance of heavy goods vehicles and trailers while the vehicle remains stationary. Powered rollers turn the wheels as the brakes are applied, allowing the tester to assess braking force (kgf), efficiency, imbalance, binding and lock-up.
Because the test is carried out under controlled and repeatable conditions, the DVSA recognises laden roller brake testing as the preferred method of assessing brake performance. Every safety inspection must include a brake performance assessment using a laden roller brake test, EBPMS data, or a decelerometer with brake temperature readings.
This article reflects the updated expectations set out in the April 2025 edition of the DVSA Guide to Maintaining Roadworthiness, including the stronger emphasis on laden testing and documented justification where loading is impractical. All quoted material below is taken verbatim from official DVSA or legislative sources.
For full official guidance, refer to the DVSA Guide to Maintaining Roadworthiness and the DVSA brake test best practice documents cited throughout this article.
Contents
- What is a Roller Brake Test?
- How is a Roller Brake Test Performed?
- What Does the Roller Brake Test Measure?
- Legal Requirements and DVSA Expectations
- First-Use Inspection: Operator Responsibility
- Why is Laden Brake Testing Important?
- Exemptions and When Risk Assessment is Required
- Understanding Your Roller Brake Test Report
- Frequently Asked Questions
- Final Thoughts
What is a Roller Brake Test?
A roller brake test measures the braking performance of each wheel while the vehicle remains stationary. The wheels sit on powered rollers, which rotate beneath the tyres. As the brakes are applied progressively, the tester records brake force, lock-up, imbalance, binding and overall efficiency.
The controlled test conditions make results consistent and repeatable. This allows operators to assess brake performance, identify defects and retain evidence that the braking system has been checked as part of the vehicle maintenance regime.
How is a Roller Brake Test Performed?
- Preparation
The vehicle is positioned on the rollers. For trailers, an external air supply may be connected. DVSA best practice expects testing at around 65% of design axle weight, unless exceptions apply. - Controlled brake application
Each axle is tested separately. The rollers rotate the wheels, the brakes are applied progressively, and the tester records force, imbalance, lock-up behaviour and binding. - Assessment
The system calculates brake efficiency and identifies mechanical or performance issues. Results are compared against the DVSA's HGV inspection standards.
What Does the Roller Brake Test Measure?
Brake Efficiency
Brake efficiency compares the braking force produced with the weight of the vehicle or axle. For heavy vehicles, the DVSA's minimum efficiencies include:
- Service brake: ≥ 50%
- Secondary brake (where assessed separately): ≥ 25%
- Parking brake: ≥ 16%
Brake Imbalance
Brake imbalance compares the braking effort produced by the wheels on the same axle. Excessive imbalance can affect vehicle stability and indicates that the brakes are not operating evenly.
“The vehicle will fail if the brake imbalance is more than 30%… unless both wheels lock.”
Brake Binding and Lock-Up
- Bind: residual brake force after the brake is released
- Lock-up: early wheel lock, often due to low axle loading
- Maximum brake force: the highest braking force recorded at each wheel
Legal Requirements and DVSA Expectations
Construction and Use Regulations
The legal requirement to maintain brake systems derives from Regulation 18 of The Road Vehicles (Construction and Use) Regulations 1986:
“Every part of every braking system and of the means of operation thereof fitted to a vehicle shall be maintained in good and efficient working order and be properly adjusted.”
Brake Performance at Every Safety Inspection
“Every safety inspection must assess the braking performance of the vehicle or trailer. There are 3 ways to check brake performance at a safety inspection:
1. Laden roller brake test – a recommended minimum of 3 a year as well as the MOT test
2. Decelerometer with brake temperature measurement for rigid vehicles
3. Electronic braking performance monitoring system (EBPMS) assessment.”
Annual Testing and Test Frequency
“You should get your HGV or trailer’s brakes tested by a roller brake tester (RBT) at least 4 times per year, including at the MOT.”
The April 2025 edition of the Guide to Maintaining Roadworthiness strengthens the emphasis on presenting vehicles laden for brake testing wherever practical.
First-Use Inspection: Operator Responsibility
The DVSA confirms that operators, rather than manufacturers, are responsible for completing the first roller brake test before using a newly acquired vehicle or trailer on the road:
“Prior to using a newly acquired vehicle on the public highway, operators must conduct a first use inspection… this includes conducting a laden roller brake test when appropriate for the type of vehicle.”
Why is Laden Brake Testing Important?
Laden testing provides better grip between the tyres and rollers, reduces premature wheel lock-up and produces more reliable efficiency measurements. Without sufficient axle loading, a wheel may lock before the braking system reaches its maximum performance, which can limit the value of the result.
“Your vehicle must be loaded for a brake test – ideally to at least 65% of its total maximum weight. It can only be tested unladen if it cannot be loaded due to design limitations or the type of load it normally carries.”
Exemptions and When Risk Assessment is Required
The DVSA's brake test best practice explains that vehicles should normally be tested laden:
“Vehicles must be fully loaded before being roller-brake tested… This normally means at least 65% of the vehicle design axle weight (DAW).”
Testing unladen is only acceptable where loading is impractical because of the vehicle design or the nature of the load, such as with some tankers or livestock vehicles. In these cases, operators must:
- Complete a written risk assessment explaining why laden testing is not possible
- Use an approved alternative method, either EBPMS or a decelerometer with brake temperature readings
- Retain all documentation for at least 15 months
The April 2025 Guide to Maintaining Roadworthiness strengthens the expectation that operators formally document and justify any departure from laden roller brake testing.
Understanding Your Roller Brake Test Report
A typical report includes brake force (kgf), imbalance, lock-up, binding, axle weights, loading status and axle configuration. These results should be checked alongside the vehicle details recorded on the report.
“The DTp number should match the one shown on the vehicle’s plating certificate. Your test result may be incorrect if it’s wrong.”
Incorrect DTp details, axle design weights, axle configuration or loading information can distort the calculated efficiencies and make the result unreliable.
Frequently Asked Questions
Who is responsible for the first roller brake test on a new trailer?
The operator is responsible. The DVSA confirms that the first-use inspection must include a laden roller brake test when appropriate for the vehicle type.
Does a trailer need to be laden for a roller brake test?
Yes. The DVSA states that the vehicle should be loaded, ideally to around 65% of its maximum weight, unless loading is impractical because of the vehicle design or load type.
How many roller brake tests are recommended per year?
DVSA guidance advises testing at least four times per year, including the MOT, unless an EBPMS is used.
Can a roller brake test be carried out unladen?
Only where loading is not feasible. The operator must document why laden testing is impractical and record the alternative brake assessment method used.
What are common reasons for roller brake test failures?
Common causes include excessive imbalance, insufficient brake force, binding, contamination, wear and problems with brake adjusters.
Final Thoughts
Roller brake testing remains the preferred method of demonstrating brake performance. Operators should use regular laden tests wherever practical, retain accurate reports and formally justify any alternative assessment method. Correct vehicle, axle and loading data are also essential for producing a reliable result.
